Complex probe card for testing a semiconductor wafer

ABSTRACT

A probe card includes a printed circuit plate having an aperture at the center thereof and a ring fixed around said aperture on either side of the plate. The ring is adapted to support probe needles in radial arrays with respect to the aperture. Each of the arrays has a multilayer of probe needles which have their terminal tips aligned on a plane in parallel with the plate and their opposite terminal ends connected to the printed circuit for external connection.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a probe card used for testingsemiconductor products, such as ICs and LSIs.

2. Description of the Prior Art

In the manufacture of IC and LSI products in which a number of waferchips are fixed on a base plate, the chips are individually tested priorto cutting them. For such testing a testing device, commonly called aprober, is employed, to which a probe card is connected. The testing iseffected by connecting the probe pins or needles of the card to theelectrodes on the semiconductor chips.

The probe cards at the earlier stage were adapted for use in testingintegrated circuits having a relative low degree of integration, or LSIshaving a relatively small number of testing terminals, and accordingly,it was sufficient that the probe cards had 48 probe needles around achip of 2 centimeters in diameter. Such a probe card is disclosed inU.S. Pat. No. 3,835,381. However, as the integrated circuits areimproved to intensify their degree of integration, it is becomenecessary to increase the number of probe needles. Recently there hasarisen a demand in the industry for fixing 300 or more probe needles inthe area of 8×8 mm. In line with this industrial trend, the number oftesting electrodes on a semiconductor wafer chip has become so vast thatthey cannot be arranged at the peripheral portion alone of the chip asunder the conventional practice, and it has become necessary to fill thewhole area of the chip with electrodes, regularly or irregularly.

The present invention is directed toward meeting such demand in theindustry, and has for its object to provide an improved probe card fortesting wafer chips for use in IC and LSI products, wherein the probecard is provided with densely arranged probe needles.

A further object of the present invention is to provide an improvedprobe card capable of testing a wafer chip filled with electrodes.

Other objects and advantages of the present invention will becomeapparent from the detailed description given hereinafter; it should beunderstood, however, that the detailed description and specificembodiments are given by way of illustration only, since various changesand modifications with the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

SUMMARY OF THE INVENTION

According to one aspect of the present invention a probe card includes aprinted circuit plate having an aperture at the center thereof and aring fixed around said aperture on either side of the plate, said ringbeing adapted to support probe needles in radial arrays with respect tosaid aperture, each of said arrays consisting of a multilayer of probeneedles, said probe needles having their terminal tips aligned on aplane in parallel with said plate and their opposite terminal endsconnected to said printed circuit for external connection.

According to another aspect of the present invention a method ofmanufacturing a probe card described in the preceding paragraphcomprises placing a first layer of probe needles in radial arrays on theinwardly declining surface of a manufacturing jig whose gradient isdecided in accordance with the desired angle of fixture of said probeneedles, and applying an applicator coated with an adhesive on itscontact surface to said first layer of probe needles on saidmanufacturing jig, said applicator having a declining surface of thesame gradient as that of said jig, allowing said adhesive to harden,repeating said procedure until the desired number of layers of probeneedles are formed, and finally mounting said multilayers of probeneedles integrally unified with said repeated application of adhesive ona supporting ring fixed on a base plate of said probe card.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross-section through a probe card according to theinvention;

FIG. 2 is a vertical cross-section on an enlarged scale of the portionindicated by II in FIG. 1;

FIG. 3 is a vertical cross-section taken along the line III--III in FIG.2;

FIG. 4 is a plan view showing a semiconductor chip and the probe card ofFIG. 1;

FIG. 5 is a vertical cross-section through an alternative embodiment ofthe invention;

FIG. 6 is a plan view showing the probe card, partly omitted, of FIG. 5;and

FIGS. 7 to 9 show a sequence of processes of manufacturing probe cardsaccording to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1 a probe card includes a base plate 1, hereinafterreferred to merely as the plate 1, in which a central aperture 2 and aring-shaped depression 3 around the aperture 2 are formed. A ring 4 isfitted in the depression 3, which ring 4 is adapted to support probeneedles 5 as described below. The plate 1 includes conductors 7 on itssurface in which the ring 4 is fixed. The probe needles are connected tothe conductors 7 at their terminal ends, and the conductors 7 are inturn connected to outside elements through bores 8. The plate 1 can bemade of epoxide glass, and the ring 4 can be made of aluminium, ceramicsor plastics coated with an insulator on its surface. The probe needles 5are normally soldered to the conductors 7. A test piece (W), such as asemiconductor wafer, is placed in contact with the terminal tips of theprobe needles 5.

Referring to FIG. 2 the shape of each of the probe needles 5 will beexplained. In the drawing the portion of each needle 5 to the left ofthe line III--III is straight and uniformly thick, but the portion tothe right thereof tapers off towards the terminal tips with a bentportion (B). A number of probe needles 5 are supported in multilayers asshown in FIG. 2; in the illustrated embodiment only three needles 5A,5B, etc., are shown for simplicity. The needles 5 are arranged in radialarrays on the ring 4, which means that each array consists of aplurality of layers. This is made possible by differentiating thelengths of the probe needles 5 between the ones in the inner layers 5Band in the outer layers 5A. In the illustrated embodiment the probeneedles 5 in the inner layers 5B are increasingly longer than the onesin the outer layers 5A. Thus it is ensured that all the terminal tips ofthe probe needles 5 are aligned on one plane in parrallel with theplate 1. The probe needles 5 in the inner layers 5B are placed intocontact with electrodes located at the center of a test piece (W), andthe ones in the outer layers 5A are placed into contact with electrodeslocated at the periphery thereof. The probe needles 5 are made oftungsten, palladium or beryllium copper. The tapering portion of eachneedle 5 is 0.2 to 0.3 mm thick. The longer needles are made thickerthan the shorter ones, so as to make the terminal tips of probe needles5 keep contact with the test piece with an equal force of contact. Underthis arrangement, when the semiconductor chip is viewed from behind theplate 1, the terminal tips of some probe needles 5 can be visuallylocated, as shown by position (C) in FIG. 4.

In a preferred embodiment a distance between the adacent two terminaltips is about 350 micron, and 184 needles are arranged in the area of6×6 (mm²).

Referring to FIG. 7, an explanation will be given about how tomanufacture the probe card:

A jig 30 includes a fixed plate 31 having a post 32 erected at itscenter, wherein the post 32 has a ring-shaped projection 33 on its topwith a circular depression therein. A supporting ring 34 is fitted tothe post 32, which supporting ring 34 has an inwardly declining surface35 on which graduations are radially formed for an index purpose. Thegradient of the declinig surface 35 is decided upon, as desired. On thetop of the ring-shaped projection 33 a Mylar mask 36 of about 0.15 mm(0.006 inch) in thickness is placed, in which the same number of holes37 are made so as to accommodate the needles 5A.

In FIG. 7 the reference numeral 5A designates the probe needles 5located at the outermost (lowermost) position in the layer. The terminalends of these needles 5A are inserted into the holes 37 produced in theMylar mask 36. In this way radial arrays of the probe needles 5A areformed along the inwardly declining surface 35 of the ring 34. At thisstage as shown in FIG. 8, a truncated applicator 39 is pressed onto thering 34. The applicator 39 has a declining surface 38 of the samegradient as that of the supporting ring 34. The declining surface 38 ofthe applicator 39 is coated with an adhesive 40 containing a partingagent. For the adhesive 40 an epoxide resin can be used. The applicator39 and the ring 34, as jointed, are heated at 70° C. to 90° C. in anelectric furnace for 2 to 3 hours, thereby allowing the adhesive 40 toharden. Then they are taken away from the electric furnace, and theapplicator 39 is disengaged from the ring 34. In this way a desirednumber of needles 5 are overlaid so as to form multilayers, wherein theneedles 5 are insulated from each other. FIG. 9 shows a situation inwhich a second layer 5B is overlaid on the first layer 5A with aninsulator located therebetween. The probe needles 5 are integrallyunified with the repeated application of adhesive 40 one layer 5B afteranother layer 5A, and are partly embedded in an adhesive layer 9 (FIG.2) placed on the supporting ring 4, wherein the adhesive 40 (FIG. 8) nolonger contains a parting agent so as to fix the probe needles 5A, 5B,etc., permanently. The adhesive 9 (FIG. 2) is allowed to harden by heat,and the jig 30 is removed. Finally, the terminal tips of the probeneedles 5 are pointed. The supporting ring 4 with the multilayers ofprobe needles 5 suspended therefrom (FIGS. 1 and 2) is fitted in thering-shaped depression 3 of the plate 1. The terminal end of each probeneedle 5 is connected to a printed circuit or any other element.

As evident from the foregoing, the probe card has thick layers of probeneedles 5, but the terminal tips of some probe needles 5 can be visuallylocated from both behind and in front of the plate 1, whereby the visualadjustment of these probe needles 5 to the electrodes on a wafer chipcan be readily made. With this visual location, the whole adjustment tothe other electrodes thereon finishes. This greatly enhances the workingefficiency.

This example of a first embodiment can be modified by providing afurther supporting ring 4 (FIG. 1) around the back of the centralaperture 2, and adding one or more layers of probe needles 5 thereto.

Referring now to FIGS. 5 and 6, a further alternative embodiment will bedescribed:

In this embodiment, a base plate 10, hereinafter referred to merely asthe plate 10, is made up of an inner plate 11 and an outer plate 15. Theinner plate 11 has a central aperture 12 and a ring-shaped depression 13in which a ring 14 is fitted for supporting probe needles 23 (FIG. 6).The outer plate 15 has an aperture 17 of sufficient area to allowconductors 16 placed on the inner plate 11 to expose each centralportion therethrough. Both apertures 12 and 17 are concentric but theaperture 17 is larger than the aperture 12. Each conductor 16 isradially fixed to the inner plate 11, and is connected to each terminalrod 19 for external connection, wherein the terminal rods 19 aresupported in bores 18 produced throughout the plates 11 and 15. Theterminal rods 19 are insulated from conductors 20 placed on the outerplate 15. It is arranged that the conductors 16 and 20 do not come intoany contact with each other. Each conductor 20 is connected to eachterminal rod 22 passing through a bore 21 produced throughout the plates11 and 15. The probe needles 23 (FIG. 6) are arranged in radial arrayson the ring 14 in the same manner as described with respect to the firstembodiment. The terminal ends of the probe needles 23 are connected tothe conductors 16 and 20. Likewise, the probe needles 23 are arranged inmultilayers by differentiating their length in the same manner asdescribed above.

For a further modified version of this second embodiment the plates 11and 15 can number more than two.

What is claimed is:
 1. A probe card for testing semiconductor waferscomprising:a printed circuit plate having an aperture at the centerthereof and a ring fixed around said aperture on a bottom side of saidprinted circuit plate, said ring having an underside with an inwardlydeclining surface, probe needles arranged in radial arrays with respectto said aperture, each of said radial arrays having multiple layers ofprobe needles, an adhesive layer for suspending said multiple layers ofprobe needles parallel to the inwardly declining surface of said ring,said probe needles having tapered terminal tips aligned on a plane inparallel with but spaced from said printed circuit plate and oppositeuniformly thick terminal ends connected to said printed circuit platefor external connection, wherein said probe needles in inner layers arelonger than said probe needles in outer layers, and wherein saidaperture is large sufficiently to allow said tapered terminal tips ofsaid probe needles to be visually located and readily adjusted from bothbehind and in front of said printed circuit plate.